Fluidic jet collectors

ABSTRACT

The invention relates to a fluidic device comprising a channel of rectangular section having a rectangular inlet orifice in one of the walls and a rectangular outlet orifice in the opposite wall; the channel acts as a vent. When fluid enters the channel through the inlet orifice, an unrestrained and irreversible expansion takes place. The expansion is accompanied by variation in local pressure due to the interaction of multiple expansion and compression waves which provide the device with a desired input/output pressure characteristic.

United States Patent Davies et al.

[45] Mar. 21, 1972 [54] FLUIDIC JET COLLECTORS [72] Inventors: Guy Edward Davies; Charles Michael Fitzmaurice, both of llford, England [73] Assignee: The Plessey Company Limited, Ilford, En-

gland [22] Filed: Mar. 25, 1970 [21] App]. No.: 22,576

[30] Foreign Application Priority Data Nov. 14, 1969 Great Britain ..55,8l0/69 [52] U.S.Cl ..l37/81.5 [51] Int. Cl. ..F15c 1/06 [58] Field ofSearch ..137/81.5

[56] References Cited UNITED STATES PATENTS 3,495,609 2/1970 Swartz ..l37/8 l .5

Jones ..137/81.5 Reader. .....l37/8l.5

Swartz ..l37/8l.5 Colston 137/8 1.5

Primary ExaminerWilliam R. Cline Attorney-Mason, Mason & Albright ABSTRACT 3 Claims, 3 Drawing Figures PATENTEDMARZI I972 3,650,285

OUTPUT PRESSURE RAT/0 Pr/Ps INPUT PRESSURE RAT/0 PS/PV ATTORNEYS FLUIDIC JET COLLECTORS The invention relates to fluidic devices.

The invention provides a jet collector comprising a vent channel defined by four walls, ajet orifice in one said wall of the channel through which a jet of fluid under pressure is arranged to pass into the channel, a collector orifice in a wall opposite said one wall for receiving a proportion of fluid which has been discharged from said jet orifice, said jet orifice being of such size as to extend substantially the whole of the distance between the remaining two walls which are substantially parallel to each other.

The invention also provides a fluidic jet collector comprising a member defining a closed channel of substantially rectangular cross section, said channel forming a vent, a rectangular jet orifice in one sidewall of the channel, the height of the orifice being substantially equal to the height of the sidewall in which it lies, a collector orifice in the sidewall of the channel opposite said first-mentioned sidewall and operative to receive a proportion of fluid which has been discharged from said jet orifice, the spacing between said two sidewalls being two to six times the width of the jet orifice, and the height of each of the sidewalls being one to three times the width of the jet orifice.

A fluidic jet collector embodying the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings in which:

FIG. 1 is a fragmentary plan view of the jet collector;

FIG. 2 is a section on the line X-X of FIG. 1; and

FIG. 3 shows an input/output pressure ratio characteristic of the jet collector of FIGS. 1 and 2.

FIG. 1 shows a jet collector (hereinafter referred to as a planar jet-collector) which has ajet nozzle 4, a collector orifice 6 and a vent channel 8. The vent channel is rectangular in section and is defined by two sidewalls 10 and 12, a floor 14 and a roof 16 (see FIG. 2). The spacing between the two sidewalls is x, while the height of the sidewalls is h. FIG. 2 shows the rectangular outlet orifice of the nozzle 4, the height of the outlet orifice being the same as the height of the sidewalls l and 12 and the width of the orifice being w. The jet nozzle normally operates in a choked condition. On leaving the plane of the nozzle the fluid undergoes an unrestrained and irreversible expansion to the local vent pressure Pv. This expansion is accompanied by significant variations in local pressure due to the interaction of multiple expansion and compression waves which are characteristic of such a flow.

FIG. 3 shows the input/output pressure ratio characteristic (curve A) of the planar jet collector of FIG. 1. Curve A shows a plot of the input pressure ratio Ps/Pv, being the ratio of the input pressure Ps (at the nozzle 4) to the pressure Pv in the vent channel 8, against the output pressure ratio Pr/Ps being the ratio of the pressure Pr at the collector orifice 8 to the input pressure Ps.

As will be seen, the characteristic (curve A) of the planar jet collector has a smoothly inclined, fairly shallow gradient.

The relationship between the dimensions h, w and x of the planar jet collector which enable the jet collector to exhibit a characteristic shown in curve A are as follows:

x=N'w, where Mis from I to 3 and N is from 2 to 6.

The characteristic of the planar jet collector will still be exhibited even if the height of the nozzle orifice is as low as 4/5h.

The planar jet collector described is advantageous as compared with jet collectors having a vent channel of generally circular section; such circular jet collectors exhibit input/output pressure ratio characteristics of the form shown in curve B and are not as suitable for use as proportional control devices as the planar jet collector described.

In a modification, a recess 18 is provided either in the floor 14 or the roof 16 immediately adjacent the nozzle orifice, the recess having an opening of comparable size to the jet nozzle orifice, such a modified planar jet collector will exhibit a characteristic which is operative over a greater range than the curve A.

It will be appreciated that the sidewalls l0 and 12 can be slightlyinclined with respect to one another to ease manufacture of the jet collector.

We claim:

1. A fluidic jet collector, comprising a member defining a closed channel of substantially rectangular cross section, said channel forming a vent, means defining a rectangular jet orifice in one sidewall of the channel, the height of the orifice being substantially equal to the height of the sidewall in which it lies, and

means defining a collector orifice in the sidewall of the channel opposite said first-mentioned sidewall and operative to receive a proportion of fluid which has been discharged from said jet orifice,

the spacing between said two sidewalls being between two and six times the width of the jet orifice, and the height of each of the sidewalls being between one and three times the width of the jet orifice.

2. A jet collector according to claim 1 including means defining a recess in the floor of said channel, said recess lying immediately adjacent said jet orifice and being of substantially the same size as said jet orifice.

3. A jet collector according to claim 1 including means defining a recess in the roof of said channel, said recess lying immediately adjacent said jet orifice and being of substantially the same size as the jet orifice. 

1. A fluidic jet collector, comprising a member defining a closed channel of substantially rectangular cross section, said channel forming a vent, means defining a rectangular jet orifice in one sidewall of the channel, the height of the orifice being substantially equal to the height of the sidewall in which it lies, and means defining a collector orifice in the sidewall of the channel opposite said first-mentioned sidewall and operative to receive a proportion of fluid which has been discharged from said jet orifice, the spacing between said two sidewalls being between two and six times the width of the jet orifice, and the height of each of the sidewalls being between one and three times the width of the jet orifice.
 2. A jet collector according to claim 1 including means defining a recess in the floor of said channel, said recess lying immediately adjacent said jet orifice and being of substantially the same size as said jet orifice.
 3. A jet collector according to claim 1 including means defining a recess in the roof of said channel, said recess lying immediately adjacent said jet orifice and being of substantially the same size as the jet orifice. 